The conventional flat-plate solar collectors are widely used in solar heating apparatus. Such a conventional collector is shown in FIG. 6 in that, the heat collected by absorber A is derived from the absorbed heat turned by straight light DL and the heat conducted from the plate R as exposed to straight sunlight DL' and inclined light IL. However, major sunlights either straight light DL' or inclined light IL are reflected from the collector plate R and only minor sunlights are absorbed by the plate R which then conducts the absorbed heat to the absorber A. Hence, the heat-collection efficiency of conventional flat-plate collector as FIG. 6 shown will be greatly reduced as reflection loss.
The conventional optical-type concentrator is shown in FIG. 7. Such a conventional configuration as FIG. 7 shown proposes a parabolic trough concentrator of which a heat pipe (absorber) A is mounted along the focal line of parabolic trough. Said trough serves as a reflective surface R. The direct straight sunlight DL will be reflected through said surface to focus on said absorber A. However, the indirect or inclined light IL will not focus on said absorber so that the collector efficiency will be deducted. If mounting said concentrator on a tracking mechanism (axis of rotation coinciding with the focal line of concentrator), the concentrator will always track the sun so that the collector efficiency will be raised. However, the initial cost to add such a tracking device will be more increased. For general applications, using such a solar collector with higher initial construction cost will not be economic.